Oxidative dehydrogenation of ethylbenzene to styrene using a gold on titania catalyst

ABSTRACT

Styrene is prepared from ethylbenzene by contacting a mixture of ethylbenzene oxygen-containing gas and an inert diluent with a catalyst consisting of gold supported on or admixed with titania, at an elevated temperature.

United States Patent [1 1 [111 3,742,079 Etherington June 26, 1973 [54]()XIDATIVE DEHYDROGENATION OF 3,156,735 11/1964 Armstrong 260/680 EETHYLBENZENE o STYRENE USING A 3,223,743 12/1965 MacFarlane 260/669 RGOLD ON TITANIA CATALYST 3,476,808 1 1/1969 Etherington et al. 260/586[75] Inventor: Robert W. Etherington, Pennington,

[73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: June 30, 1971 [21] Appl. No.2 158,535

[52] U.S. Cl 260/669 R [51] Int. Cl. C07c 15/10 [58] Field of Search260/669 R, 680 E [56] References Cited UNITED STATES PATENTS 3,553,2201/1971 Etherington et a1. 260/290 Primary ExaminerCurtis R. DavisAttorney- Oswald G. Hayes, Hastings S. Trigg et a1.

[57] ABSTRACT 5 Claims, No Drawings OXIDATIVE DEIIYDROGENATION OFETI-IYLBENZENE TO STYRENE USING A GOLD ON TITANIA CATALYST BACKGROUND OFTHE INVENTION 1. Field of the Invention The present invention provides aprocess for the oxidative dehydrogenation of ethylbenzene to styrene.

2. Description of the Prior Art It has been proposed to carry out anoxidative dehydrogenation reaction using a catalyst comprising gold on alow surface area inert support. Such patents are directed to oxidativedehydrogenation of ketones (U. S. Pat. No. 3,476,808) and alkylpyridines (U. S. Pat. No. 3,553,220). In U. S. Pat. No. 3,156,735, it isproposed to carry out oxidative dehydrogenation using as the catalyst agold alloy with a platinum or palladium metal on a low surface areasupport. Dehydrogenation (not oxidative) of ethylbenzene to styrene isshown, in U. S. Pat. No. 3,233,743, to be carried out using iron,titanium or vanadium oxide promoted with an alkali metal salt.

SUMMARY OF THE INVENTION This invention provides a process for preparingstyrene that comprises contacting a mixture of ethylbenzene,oxygen-containing gas, and an inert diluent gas with a gold on titaniacatalyst at temperatures of between about 400 C. and about 800 C.

DESCRIPTION OF SPECIFIC EMBODIMENTS The initial reactant in the processof this invention is ethylbenzene which is readily availablecommercially. It is also readily prepared as, for example, by alkylatingbenzene with ethylene. The ethylbenzene is charged to the process at anLI-ISV (the rate of liquid ethylbenzene charge per volume of catalystper hour) of between about 0.1 and about 10, preferably between about0.3 and about 3.

The oxygen-containing gas can be pure oxygen or gaseous mixturescontaining oxygen such as air or mixtures of oxygen and nitrogen. Themolar ratio of oxygen to ethylbenzene will be between about 0.01 andabout 3, preferably between about 0.1 and about 1.0.

The preferred diluent is nitrogen or steam. Other inert diluent gasescan be used, however, e.g., carbon dioxide or flue gas.

The catalyst used in the process of this invention is gold on titania(TiO The amount of gold in the catalyst, based upon the weight of thefinished catalyst, will be between about 0.01 weight percent and 50weight percent, preferably between about 0.05 weight percent and aboutweight percent. In general, any method known in the art for preparingsupported metallic catalyst can be used. A particularly preferredmethod, used for preparing the catalysts in the examples, was toimpregnate the surface of the titania with a solution of gold t-dodecylmercaptide and a bismuth resinate flux dissolved in a mixture of estersand tall oil (a so-called liquid gold") followed by calcining. Thisoperation is repeated until the desired amount of gold is obtained.Other methods of preparation may be used, such as coating titania withother gold derivatives and calcining, or depositing the gold on titaniapowder and then forming the catalyst particles and calcining, or bycoprecipitating metallic gold and titania hydrogel followed by formingcatalyst particles and calcining. Another method is to impregnate ashaped titania particle with a gold salt and calcining to the metallicgold.

The temperature of reaction, i.e., the temperature of the catalyst bedwill be between about 400 C. and about 800 C., preferably between about550 C. and about 775 C. The reaction can be readily carried out atatmospheric pressure. It has been found, however, that processadvantages may be realized by using a pressure of about 10 to 150p.s.i.g.

The following Examples illustrate the process of this invention. In allthe examples, ethylbenzene was pumped to a vaporizer and the vapors weremixed with a stream of air and of a diluent consisting of nitrogen orsteam. The resulting mixture was passed through a pre-heater zone packedwith inert pellets and then through a cc. bed of catalyst packed in a iinch I.D., stainless steel pipe reactor containing a concentric A inchO.D. thermowell. The reactor was mounted vertically and the reactantsflowed in a downward direction. The reactor was heated with an electricfurnace. The

exit gas mixture was passed through a series of condensers and liquidproducts were collected. The liquid products were analyzed by gas-liquidchromatography. All conversions and selectivities reported are in molepercent.

EXAMPLE I Ethylbenzene was fed to the reactor at the rate of 60.7 g./hr.along with air, 500 cc. per minute, and nitrogen diluent, l500 cc. perminute. The catalyst consisted of 4% Au on A; inch titania pellets of 65m /gram surface area. The maximum temperature in the catalyst bed was700 C. The liquid products contained 49.8 mole percent styrene, 47.1%ethylbenzene, 1.7% benzene, and 1.5% toluene. Ethylbenzene conversionwas 52.9 percent and the selectivity was 94.0 percent to styrene.

EXAMPLE 2 When Example 1 was repeated with the maximum temperature inthe catalyst bed raised to 750 C., the ethylbenzene conversion was 68.7percent and the selectivity to styrene was 87.5 percent.

EXAMPLE 3 When Example 2 was repeated with air flow lowered to 250 cc.per minute and nitrogen flow raised to 1,750 cc. per minute, theethylbenzene conversion was 61.4 percent and the selectivity to styrenewas 90.8 percent.

EXAMPLE 4 When Example 3 was repeated with the pressure in the reactorraised to 15 p.s.i.g., the ethylbenzene conversion was 65.8 percent andthe selectivity to styrene was 92.6 percent.

EXAMPLE 5 Under the conditions of Example 1, but using a catalystconsisting of 1 percent gold on titania, the conversion of ethylbenzenewas 57.3 percent and selectivity to styrene was 95.9 percent.

was raised to 750 C., the ethylbenzene conversion was 68.2 percent andthe selectivity to styrene was 92.7

EXAMPLE Using steam as the diluent (70 g. H O/hour), 60.7 g.

ethylbenzene per hour and 500 cc. of air per minute over a 1 percentAu-titania catalyst at p.s.i.g. reacpercent. tor pressure, a 59.2percent ethylbenzene conversion At 775 C. the ethylbenzene conversionwas 71.6 was obtained at 700 C. with 88.6 percent selectivity to percentand selectivity to styrene was 89.9 percent. styrene.

At 750 C. the conversion of ethylbenzene was 71.5 EXAMPLE 7 10 percentand the selectivity to styrene was 89.0 percent.

When the conditions of Example 1 were used with EXAMPLE H the unmodifiedtitania as catalyst, the ethylbenzene I conversion was 36.7 percent andthe selectivity to sty- When the experiment of Example 2 was repeatedrene was 87.7 percent. using a 0.5 percent Au on titania catalyst theethylben- When the maximum catalyst temperature was raised 15 zeneconversion was 70.0 percent and the selectivity to to 750 C., theethylbenzene conversion was 59.9 perstyrene was 85.7 percent. cent andselectivity to styrene was 79.9 percent. At 700 C. the ethylbenzeneconversion was 57.0

ercent and the selectivit to st rene was 93.5 ercent. EXAMPLE 8 p y y PEXAMPLE 12 Under the conditlons of Example 1, a catalyst consisting of2.2 percent All deposited on fused alumina when a 0,1 percent Au ontitania Qatalyst was used Spheres f -1 lggave only 19.4 percentconversion under the conditions of Example 1, the ethylbenzene ofethylbenzene with 82.0 percent selectivity to styconversion was 62.1percent and the selectivity to styrene. rene was 92.9 percent.

When the maximum catalyst temperature was raised At a m im m temperatureof 725 C. the ethylbento 750 C. the conversion of ethylbenzene rose to 5-6 zene conversion was 69.7 percent and the selectivity to percent butselectivity to styrene was only 70.9 per-' styrene was 90.7 percent.cent. For more ready reference, the runs described in the foregoingExamples are presented in tabular form. EXAMPLE 9 Table 1 presentspertinent data on the runs carried 00': Under the conditions of Example1, a catalyst conusing the catalyst of this invention.

' TABLE 1 Au on T107 Feed Catalyst Percent Ethyl- Percent benzene, Air,Nitrogen, Temp, Conver- Selectiv- Styrene Au Carrier g./hr. ccJmin.cc./1nin. C. sion ity per pass 1 T102 00.7 500 1,500 700 52.0 04.0 40.74 T102 00.7 500 1,500 750 00.7 07.5 00.1 4 T105 00.7 250 1,750 750 01.400.0 55.0 T105 00.7 250 1,500 750 05.0 02.0 00.0 1 T10: 00.7 500 1,500700 57.5 05.0 55.0 1 T101 00.7 500 1,500' 750 68.2 02.7 v 03.3 1 T 00.7500 1,500 775 71.0 00.0 04.4 1 T10: 00.7 500 700 50.2 00.0 52.5 1 T 00.7500 750 71.5 89.0 03.0: 05 T10: 00.7 500 1,500 750 70.0 05.7 00.0 0.5T10: 00.7 500 1,500 700 57.0 03.5 53.3 0.1 T102 00.7 500 1,500 700 02.102.0 57.7 01 T10; 00.7 500 1,500 725 00.7 00.7 03.2

1 Pressure was 15 p.s.i.g.

2 Dlluent was steam.

sisting of 10 percent gold deposited on active alumina (-210' mlgram)gave 36.8 percent conversion but only 78.2 percent selectivity tostyrene.

When the maximum catalyst temperature was raised to 750 C., thiscatalyst gave 58.1 percent ethylbenzene 55 conversion but only 71.6percent selectivity to styrene.

It will be noted that in all runs conversion and selectivity were bothquite high. It is also to be notedthat the percent of styrene obtainedper pass was about 50 percent or higher. Table 11 presents pertinentdata for runs carried out using catalysts other than those of thepresent invention.

TABLE '11 Other Catalysts Feed Catalyst Percent Ethyl- Percentbenzene,Air, Nitrogen Temp, Conver- Selectiv- Styrene Example Au Carrier g./hr.ecu/min. ccJrnin. C. sicn ity per pass 7 None T10; 60. 7 500 1, 500 70036. 7 87. 7 32. 2 None T105 60. 7 500 1, 500 750 59. 9 79. 9 47. J 8 2A1203 60. 7 500 1, 500 700 19. 4 82. 0 15. 9 2 A1203 60. 7 500 1, 500750 54. 6 70. ll 38. 7 9 10 A1200 60. 7 500 1, 500 700 36. 8 78. 2 28. 810 A1203 60. 7 500 1, 500 750 58. 1 71. 6 41. 6

From the data in Table II, it will be noted that with titania alone,unmodified by gold, conversion and selectivity were low and the amountof styrene obtained per pass was less than 50 percent. Using gold onalumina, as shown in prior patents, the results were unsatisfactory, ascompared to the results shown in Table l.

It will be appreciated, therefore, that the use of gold on titaniaspecifically produces results that are not obtainable with othercatalysts. It is another feature of this invention that the titaniasupport should have a relatively high surface area in the order ofbetween about 5 and about 100 m /g.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand.

Such modifications and variations are considered to be within thepurview and scope of the appended claims.

What is claimed is: l. A process for preparing styrene that comprisescontacting a mixture of ethylbenzene, molecular oxy-

2. The process of claim 1, wherein the process is carried out at apressure of about 10 to about 150 p.s.i.g.
 3. The process of claim 2,wherein said molecular oxygen-containing gas is air.
 4. The process ofclaim 3, wherein said inert gas is nitrogen.
 5. The process of claim 3,wherein said inert gas is steam.